Tape measure with tear resistant tape blade edge

Abstract

A tape measure including a tape measure blade having an edge design to increase tape blade durability is provided. The metal portion of the tape blade may include lateral edge surface sections that have a non-planar, tear reducing shape. The metal portion of the tape blade may include lateral edge surface sections that include a tear reducing surface treatment such as a polished lateral edge surface section.

What is claimed is: 
     
       1. A tape measure comprising:
 a housing: 
 a reel rotatably mounted within the housing; 
 an elongate blade wound around the reel, the elongate blade comprising:
 an elongate metal core having an upper surface, a lower surface, a first lateral edge surface extending between the upper and lower surfaces of the elongate metal core and a second lateral edge surface opposite the first lateral edge surface and extending between the upper and lower surfaces of the elongate metal core; 
 wherein the upper surface of the elongate metal core includes a concave curved section; 
 wherein the lower surface of the elongate metal core includes a convex curved section; 
 wherein the first lateral edge surface includes a convex curved section; 
 wherein the second lateral edge surface includes a convex curved section; 
 wherein the convex curved section of the first lateral edge surface defines an arc having an angle of 60 to 120 degrees, wherein the convex curved section of the second lateral edge surface defines an arc having an angle of 60 to 120 degrees; and 
 
 a retraction mechanism coupled to the reel configured to drive rewinding of the elongate blade on to the reel. 
 
     
     
       2. The tape measure of  claim 1 , wherein the convex curved section of the first lateral edge surface is a continuous curved section extending from the upper surface to the lower surface of the elongate metal core, wherein the convex curved section of the second lateral edge surface is a continuous curved section extending from the upper surface to the lower surface of the elongate metal core. 
     
     
       3. The tape measure of  claim 2 , wherein the convex curved section of the first lateral edge surface extends lengthwise an entire length of the elongate metal core, wherein the convex curved section of the second lateral edge surface extends lengthwise the entire length of the elongate metal core. 
     
     
       4. The tape measure of  claim 1 , wherein the elongate blade further comprises a polymer coating coupled to the elongate metal core. 
     
     
       5. The tape measure of  claim 4 , wherein the polymer coating is located both above the upper surface of the elongate metal core and below the lower surface of the elongate metal core. 
     
     
       6. The tape measure of  claim 5 , wherein the polymer coating does not cover the first lateral edge surface or the second lateral edge surface. 
     
     
       7. The tape measure of  claim 1 , wherein a section of the first lateral edge surface is polished such that an average number of surface defects per unit of area of the first lateral edge surface is less than an average number of surface defects per the unit of area of the upper surface of the elongate metal core. 
     
     
       8. The tape measure of  claim 7 , wherein the polished section of the first lateral edge surface is located only within the first 10 feet of length of the elongate metal core adjacent to a hook assembly coupled to an outer end of the elongate blade. 
     
     
       9. The tape measure of  claim 1 , wherein the retraction mechanism comprises a spring coupled to the reel such that when the elongate blade is unwound from the reel to extend from the housing the spring stores energy and the spring releases energy driving rewinding of the elongate blade on to the reel. 
     
     
       10. The tape measure of  claim 9 , wherein the elongate metal core has a thickness, T 1 , measured between the upper surface and the lower surface, wherein T 1  is between 0.09 mm and 0.2 mm. 
     
     
       11. A tape measure comprising:
 a housing: 
 a reel rotatably mounted within the housing; 
 an elongate metal tape blade core wound on the reel, the elongate metal tape blade core comprising:
 an upper surface; 
 a lower surface; 
 a first lateral edge surface extending between the upper and lower surfaces of the elongate metal core; and 
 a second lateral edge surface opposite the first lateral edge surface and extending between the upper and lower surfaces of the elongate metal tape blade core; 
 wherein the first lateral edge surface of the elongate metal tape blade core include a curved longitudinal cross-sectional shape located between the upper surface and the lower surface; 
 wherein the second lateral edge surface of the elongate metal tape blade core include a curved longitudinal cross-sectional shape located between the upper surface and the lower surface; and 
 
 a retraction mechanism coupled to the reel configured to drive rewinding of the elongate metal tape blade core on to the reel. 
 
     
     
       12. The tape measure of  claim 11  further comprising:
 a coating layer coupled to the elongate metal tape blade core; 
 wherein the upper surface of the elongate metal tape blade core includes a concave curved section; 
 wherein the lower surface of the elongate metal tape blade core includes a convex curved section. 
 
     
     
       13. The tape measure of  claim 12 , wherein the coating layer is a polymer coating located both above the upper surface of the elongate metal tape blade core and below the lower surface of the elongate metal tape blade core. 
     
     
       14. The tape measure of  claim 11 , wherein the curved longitudinal cross-sectional shape of the first lateral edge surface is a continuous curved section extending from the upper surface to the lower surface of the elongate metal tape blade core, wherein the curved longitudinal cross-sectional shape of the second lateral edge surface is a continuous curved section extending from the upper surface to the lower surface of the elongate metal tape blade core. 
     
     
       15. The tape measure of  claim 14 , wherein the curved longitudinal cross-sectional shape of the first lateral edge surface extends lengthwise an entire length of the elongate metal tape blade core, wherein the curved longitudinal cross-sectional shape of the second lateral edge surface extends lengthwise the entire length of the elongate metal tape blade core. 
     
     
       16. The tape measure of  claim 11 , wherein the curved longitudinal cross-sectional shape of the first lateral edge surface defines an arc having an angle 45 degrees to 180 degrees, wherein curved longitudinal cross-sectional shape of the second lateral edge surface defines an arc having angle 45 degrees to 180 degrees. 
     
     
       17. A tape measure comprising:
 a housing: 
 a reel rotatably mounted within the housing; 
 an elongate tape measure blade wound around the reel comprising an elongate metal core, the elongate metal core comprising:
 an upper surface; 
 a lower surface; 
 a first lateral edge surface extending between the upper and lower surfaces of the elongate metal core; and 
 a second lateral edge surface opposite the first lateral edge surface and extending between the upper and lower surfaces of the elongate metal core; 
 wherein the first lateral edge surface includes a surface finish such that a characteristic of the first lateral edge surface is different than a characteristic of the of the upper surface of the elongate metal core; 
 wherein the second lateral edge surface includes a surface finish such that a characteristic of the second lateral edge surface is different than a characteristic of the of the upper surface of the elongate metal core; and 
 
 a retraction mechanism coupled to the reel configured to drive rewinding of the elongate tape measure blade on to the reel. 
 
     
     
       18. The tape measure of  claim 17 , further comprising a hook assembly coupled to an outer end of the elongate tape measure blade, wherein the surface finishes of the first lateral edge surface and of the second lateral edge surface are located only within the first 10 feet of length of the elongate tape measure blade adjacent to the hook assembly. 
     
     
       19. The tape measure of  claim 17 , wherein the upper surface of the elongate metal core includes a concave curved section, wherein the lower surface of the elongate metal core includes a convex curved section, wherein the first lateral edge surface includes a convex curved section, wherein the second lateral edge surface includes a convex curved section. 
     
     
       20. The tape measure of  claim 17 , further comprising a polymer layer coupled to the elongate metal core, and a hook assembly coupled to an outer end of the elongate tape measure blade.